Creating Rational Functions out of asymptotes

Hi. I was wondering if anyone knew how to give an example of a rational function that has a horizontal asymptote at y = 1 and a vertical asymptote at x = 4? My book doesn't explain it very well and I can't find any tutorials on the internet. If you are able to, you could please give a small explanation of how you did it so that I can try to figure out how to do the rest of them?